Air Pollution Can Amplify Negative Effects of Climate Change

The impacts of air pollution on human health, economies and agriculture differ drastically depending on where on the planet the pollutants are emitted, according to a new study that could potentially incentivize certain countries to cut climate-changing emissions.

Led by The University of Texas at Austin and the University of California San Diego, the study is the first to simulate how pollutants affect both climate and air quality for locations around the globe.

Geeta Persad

The research, which is published in Science Advances, analyzed the climate and air quality impacts of aerosols — tiny solid particles and liquid droplets that contribute to smog and are emitted from industrial factories, power plants and vehicle tailpipes. Aerosols create unique global patterns of impact on human health, agricultural and economic productivity when compared with carbon dioxide (CO2) emissions, which are the focus of efforts to mitigate climate change.

Although CO2 and aerosols are often emitted at the same time during the combustion of fuel, the two substances behave differently in Earth’s atmosphere, said co-lead author Geeta Persad, an assistant professor in UT Austin’s Jackson School of Geosciences.

“Carbon dioxide has the same impact on climate no matter who emits it,” Persad said. “But for these aerosol pollutants, they tend to stay concentrated near where they’re emitted, so the effect that they have on the climate system is very patchy and very dependent on where they’re coming from.”

The researchers found that, depending on where they are emitted, aerosols can worsen the social costs of carbon – an estimate of the economic costs greenhouse gases have on society — by as much as 66%.

The scientists looked at eight key regions: Brazil, China, East Africa, western Europe, India, Indonesia, the United States and South Africa.

“This research highlights how the harmful effects of our emissions are generally underestimated,” said Jennifer Burney, co-lead author and the Marshall Saunders Chancellor’s Endowed Chair in Global Climate Policy and Research at the UC San Diego School of Global Policy and Strategy. “CO2 is making the planet warmer, but it also gets emitted with a bunch of other compounds that impact people and plants directly and cause climate changes in their own right.”

The work, which was supported by the National Science Foundation, represents a collaboration between Persad and Burney, who are physical scientists, and a group of economists and public health experts. Co-authors include Marshall Burke, Eran Bendavid and Sam Heft-Neal at Stanford University and Jonathan Proctor at Harvard University.

Aerosols can directly affect human health and the climate on their own. They are associated with negative health impacts when inhaled and can affect the climate by influencing temperature, precipitation patterns and how much sunlight reaches the Earth’s surface.

To study aerosols’ influence in comparison to CO2, the team created a set of climate simulations using the Community Earth System Model version 1 developed by the National Center for Atmospheric Research. They ran simulations in which each of the eight regions produced identical aerosol emissions and mapped how temperature, precipitation and surface air quality were affected across the globe. Then they connected this data with known relationships between climate and air quality and infant mortality, crop productivity, and gross domestic product across the eight regions. Finally, they compared the total societal costs of these aerosol-driven impacts against the societal costs of CO2 emitted in each of the eight regions.

The outcome paints a varied and complicated picture. Emissions from some regions produce climate and air quality effects that range from two to more than 10 times as strong as others and social costs that sometimes affect neighboring regions more than the region that produced the aerosol emissions. For example, in Europe local emissions result in four times as many infant deaths outside Europe as within.

But the researchers note that aerosol emissions are always bad for both the emitter and the planet overall.

“While we might think about aerosols, which cool the climate, as having the silver lining of counteracting CO2-driven warming, when we look at all these effects in combination, we find that no region experiences overall local benefits or generates overall global benefits by emitting aerosols,” Persad said.

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